1. Field of the Invention
The present invention relates to a rear-projection type imaging device which reflects an optical image projected from a projection unit and projects the image onto a screen which is provided exposed on one side of a housing, and more particularly, to a rear-projection type imaging device which shares at least a projection unit and a base cabinet incorporating principal components such as various control substrates which control the projection unit so as to make the screen size selectable.
2. Description of the Related Art
Conventionally, as a rear-projection type imaging device, one described in Japanese Patent Laid-Open Publication No. 2003-337377 (patent document 1) is known. The rear-projection type imaging device disclosed here incorporates a projection unit which modulates a beam projected from a lamp unit according to image information, forms an optical image and projects an enlarged image of the optical image, a reflecting mirror which reflects the projected image and a screen which projects the optical image reflected from the reflecting mirror in a box-shaped housing, and projects the optical image reflected from the reflecting mirror onto the screen.
However, there are a plurality of inch sizes for each screen of this type of rear-projection type imaging device and when this inch size changes, the size of the housing which houses this imaging device also changes. However, providing various types of housing according to the size of the screen results in low productivity and a cost increase, and therefore Japanese Patent No. 3381181 (patent document 2) proposes a rear-projection type imaging device which forms a rear-projection type imaging device divided into two parts; an upper cabinet and lower cabinet, provides a screen and a reflecting mirror in the upper cabinet, provides principal components as a television such as an imaging apparatus, drive and control circuits, a projection unit including a projection lens and a light source in the lower cabinet, and is constructed in such a way as to make it possible to select a screen set in the upper section and the size of the upper cabinet which accommodates the screen by adjusting the focus of the projection lens. Furthermore, Japanese Patent Laid-Open Publication No. 2001-54039 (patent document 3) proposes a rear-projection type imaging device including a lower cabinet, a lower back cover surrounding the lower cabinet, a chassis section provided with a speaker device, an optical unit and a control circuit, an upper cabinet, a projection section provided with an upper back cover surrounding the upper cabinet, a screen and a reflecting mirror, capable of sharing the chassis section which fixes principal components such as various control substrates which controls the projection unit irrespective of the inch size of the screen.
The rear-projection type imaging device shown in the patent document 2 provides a plurality of types of upper cabinets provided with screens of different sizes and selectively combines them with the lower cabinet to thereby share the lower cabinet to which the principal components are fixed. Furthermore, the patent document 3 can share the chassis section provided with an optical unit and control circuit. However, according to the patent document 2, as the size of the screen increases, the width of the upper cabinet provided with this screen also increases, and therefore when the width of the lower cabinet is set according to the width of the upper cabinet mounted with a screen of a minimum size, the width of the lower cabinet differs from the width of the upper cabinet as the size of the screen increases. For this reason, the upper cabinet extends outward from both sides of the lower cabinet, not making a good appearance from the standpoint of the design. On the other hand, the patent document 3 can share the chassis section and principal components including a projection unit mounted in the chassis section, but cannot share the lower cabinet with which they are combined, and therefore it is necessary to manufacture a lower cabinet for every inch size and the degree of compatibility among parts is low, which leads to a problem of increasing the manufacturing cost as well.